Abingworth LLP [Member] Abingworth Limited Liability Partnership [Member] Abingworth LLP Accounts Payable and Accrued Liabilities [Line Items] Accounts Payable And Accrued Liabilities [Line Items] Accounts Payable and Accrued Liabilities [Line Items] Accounts Payable and Accrued Liabilities [Table] Accounts Payable And Accrued Liabilities [Table] Accounts Payable and Accrued Liabilities [Table] Accounts Payable Current Accounts payable Discloses the breakout of accrued expenses and other liabilities that are not individually material for a separate caption on the statement of financial position between the current portion (payable within 12 months of year end or the operating cycle) and non-current (payable after 12 months from year end). Accrued Expenses And Other Liabilities Disclosure [Text Block] Accrued Expenses and Other Liabilities Accrued Liabilities And Other Liabilities Accrued expenses and other liabilities Accrued expenses and other liabilities Accrued Research and Development Expense, Current Accrued Research And Development Expense Current Research and development expenses Accumulated Depreciation Depletion And Amortization Property Plant And Equipment Accumulated depreciation and amortization Additional Paid In Capital Common Stock Additional paid-in capital Additional Paid In Capital [Member] Additional Paid-in Capital Additional Percentage Interest Rate Penalty Additional Percentage Interest Rate Penalty Additional interest rate on notes per annum Additional Square Feet Leased Additional Square Feet Leased Additional office space leased (in square feet) Adjustment For Amortization Amortization expense Adjustments To Additional Paid In Capital Other Transfer of fair value of warrants exercised from liabilities to equity Adjustments To Additional Paid In Capital, Resulting From Conversion Of Convertible Debt Into Equity Adjustments To Additional Paid In Capital Resulting From Conversion Of Convertible Debt Into Equity Conversion option contained in exchangeable notes Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value Stock-based compensation Adjustments To Additional Paid In Capital Tax Effect From Share Based Compensation Tax benefits realized from stock-based compensation Adjustments To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities [Abstract] Adjustments to reconcile loss to net cash used in operating activities: Advances On Inventory Purchases Advance payment made under the agreements Agreement Expiration Date Agreement Expiration Date Agreement expiration date Amarin Pharmaceuticals Ireland Limited [Member] Amarin Pharmaceuticals Ireland Limited [Member] Amarin Pharmaceuticals Ireland Limited Amendment Flag Amendment Flag American Depositary Share [Member] American Depositary Share [Member] American Depositary Share American Depository Share [Member] American Depository Share [Member] American Depository Share American Depository Shares [Member] American Depository Shares [Member] American Depository Shares American Depository Shares to Shares Ratio American Depository Shares To Shares Ratio Number of shares that each ADS represents Amortization Of Debt Discount Premium Interest expense, amortization of discount Amortization Of Financing Costs And Discounts Amortization of debt discount and debt issuance costs Amortization Of Intangible Assets Amortization expense Amortization of Intangible Asset Amr One Hundred One [Member] Amr One Hundred One [Member] Amr One Hundred One Assets TOTAL ASSETS Assets [Abstract] ASSETS Assets Current Total current assets Assets Current [Abstract] Current Assets: Assets Fair Value Disclosure [Abstract] Asset: Award Type [Axis] Award Type [Axis] Bedminster [Member] Bedminster [Member] Bedminster Biopharmaceutical [Member] Biopharmaceutical [Member] Biopharma Bridge Loan [Member] Bridge Loan Business Acquisition Acquiree [Domain] Business Acquisition, Acquiree [Domain] Business Acquisition [Axis] Business Acquisition Business Developments [Axis] Business Developments [Axis] Business Developments Business Developments [Domain] Business Developments [Domain] Business Developments [Domain] Capitalized Computer Software Gross Software Capital Lease Obligations Total principal obligations Capital Lease Obligations Current Less: current portion Capital Lease Obligations Noncurrent Long-term capital lease Capital Leases Future Minimum Payments Due Total Capital Leases Future Minimum Payments Due [Abstract] Capital Capital Leases Future Minimum Payments Due Current 2013 Capital Leases Future Minimum Payments Due In Three Years 2015 Capital Leases Future Minimum Payments Due In Two Years 2014 Capital Leases Future Minimum Payments Interest Included In Payments Less: interest Cash And Cash Equivalents At Carrying Value CASH AND CASH EQUIVALENTS, END OF PERIOD CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD Cash and cash equivalents Cash And Cash Equivalents Fair Value Disclosure Cash equivalents-money markets Cash And Cash Equivalents Period Increase Decrease NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS Cash And Cash Equivalents Policy [Text Block] Cash and Cash Equivalents Cash [Member] Cash Cash Paid During Period For [Abstract] Cash Paid During Period For [Abstract] Cash paid during the year for: Change In Control Obligations Change In Control Obligations Change of control obligation Chemport [Member] Chemport [Member] Chemport Class Of Stock [Domain] Class of Stock [Domain] Class Of Warrant Or Right [Axis] Class of Warrant or Right Class Of Warrant Or Right Common Stock Exchange Ratio Class Of Warrant Or Right Common Stock Exchange Ratio Number of ADS that can be purchased for each warrant received Class Of Warrant Or Right [Domain] Class of Warrant or Right [Domain] Class Of Warrant Or Right Exercise Price Of Warrants Or Rights Exercise Price Class of Warrant or Right, Expiration Date Class Of Warrant Or Right Expiration Date Expiration Date Class of Warrant or Right, Fair Value Assumption, Expected Life Class Of Warrant Or Right Fair Value Assumption Expected Life Warrant derivative liability valuation assumptions, remaining term Class of Warrant or Right, Fair Value Assumption, Risk Free Interest Rate Class Of Warrant Or Right Fair Value Assumption Risk Free Interest Rate Warrant derivative liability valuation assumptions, risk-free rate Class of Warrant or Right, Fair Value Assumption, Stock Volatility Class Of Warrant Or Right Fair Value Assumption Stock Volatility Warrant derivative liability valuation assumptions, volatility rate Class of Warrant or Right, Issued Class Of Warrant Or Right Issued Number of warrants issued Class Of Warrant Or Right [Line Items] Class of Warrant or Right [Line Items] Class Of Warrant Or Right Number Of Securities Called By Warrants Or Rights Warrants issued, number of shares called by the warrant Class Of Warrant Or Right Outstanding Amount Number of warrant outstanding Class Of Warrant Or Right [Table] Class of Warrant or Right [Table] Class of Warrant or Right, Term Class Of Warrant Or Right Term Warrant term Commitments And Contingencies Commitments and contingencies (Note 9) Commitments and Contingencies Disclosure [Line Items] Commitments And Contingencies Disclosure [Line Items] Commitments and Contingencies Disclosure [Line Items] Commitments and Contingencies Disclosure [Table] Commitments And Contingencies Disclosure [Table] Commitments and Contingencies Disclosure [Table] Commitments And Contingencies Disclosure [Text Block] Commitments and Contingencies Commitments [Member] Anticipated investment before the end of 2012 Commitments To Purchase Or Fund Investments Commitments To Purchase Or Fund Investments Minority share equity investment commitment Common Stock [Member] Common Shares Common Stock Par Or Stated Value Per Share Common stock, par Common stock, par value Common Stock Shares Issued Common stock, issued Common Stock Shares Outstanding Common stock, outstanding Common Stock Value Common stock, £0.50 par value, unlimited authorized; 150,360,933 issued, 150,340,854 outstanding at December 31, 2012; 135,832,542 issued, 135,812,463 outstanding at December 31, 2011 Compensation And Employee Benefit Plans [Text Block] Defined Contribution Plans Computer Equipment and Capitalized Software [Member] Computer Equipment And Capitalized Software [Member] Computer equipment and software Computer equipment, Gross Computer Equipment Gross Computer equipment Concentrations Of Credit Risk Policy [Text Block] Concentrations Of Credit Risk Policy [Text Block] Concentration of Credit Risk Consolidation Policy [Text Block] Principles of Consolidation Construction In Progress Gross Construction in Progress Contract Termination [Member] Contract Termination Convertible Debt Convertible senior notes, carrying amount net of unamortized discount Convertible Debt [Member] Convertible Debt Current Federal Tax Expense Benefit Federal-U.S. Current Fiscal Year End Date Current Fiscal Year End Date Current Income Tax Expense Benefit Total Current Current Income Tax Expense Benefit [Abstract] Current: Current State And Local Tax Expense Benefit State-U.S. Debt Conversion By Unique Description [Axis] Debt Conversion by Unique Description Debt Conversion Converted Instrument Shares Issued 1 Convertible senior notes, total ADS into which the debt is exchangeable Debt Conversion Name [Domain] Debt Conversion, Name [Domain] Debt Conversion Original Debt Amount 1 Bridge notes converted in conjunction with the private placement, amount Debt Disclosure [Line Items] Debt Disclosure [Line Items] Debt Disclosure [Line Items] Debt Disclosure [Table] Debt Disclosure [Table] Debt Disclosure [Table] Debt Disclosure [Text Block] Debt Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument Call Date Earliest Convertible senior notes, earliest redemption date Debt Instrument Convertible Conversion Price 1 Bridge notes converted in conjunction with the private placement, price per share Debt Instrument Convertible Conversion Ratio Convertible senior notes, exchange rate of ADS per $1,000 principal amount of notes Debt Instrument Convertible Effective Interest Rate Effective interest rate Debt Instrument Convertible Remaining Discount Amortization Period 1 Debt discount amortization period Debt Instrument Date Of First Required Payment 1 Convertible senior notes, payment start date Debt Instrument Face Amount Convertible senior notes, principal amount Debt Instrument Fair Value Fair value of the liability component Debt Instrument Interest Rate Stated Percentage Convertible senior notes, stated interest rate Debt Instrument Maturity Date Convertible senior notes, maturity date Debt Instrument Maturity Date Year Debt Instrument Maturity Date Year Convertible senior notes, due date Debt Instrument Maturity Period Debt Instrument Maturity Period Note, estimated remaining life Debt Instrument Name [Domain] Debt Instrument, Name [Domain] Debt Instrument, Redemption Price Debt Instrument Redemption Price Convertible senior notes, repurchase price at option of the issuer Debt Instrument Unamortized Discount Unamortized debt discount Debt Issuance Costs Policy [Text Block] Debt Issuance Costs Policy [Text Block] Debt Issuance Costs Debt Offering [Member] Debt Offering [Member] Debt Offering Debt Policy [Text Block] Debt Instruments Deferred Federal Income Tax Expense Benefit Federal-U.S. Deferred Foreign Income Tax Expense Benefit Ireland and United Kingdom Deferred Income Tax Expense Benefit Deferred income taxes Total Deferred Deferred Income Tax Expense Benefit [Abstract] Deferred: Deferred State And Local Income Tax Expense Benefit State-U.S. Deferred Tax Assets, Depreciation and Amortization Deferred Tax Assets Depreciation And Amortization Depreciation Deferred Tax Assets Gross Net deferred tax asset Deferred Tax Assets Net Deferred Tax Assets, Net of Valuation Allowance, Total Deferred Tax Assets Net [Abstract] Deferred tax assets: Deferred Tax Assets Net Current Deferred tax asset Deferred Tax Assets Net Noncurrent Deferred tax asset Deferred Tax Assets Operating Loss Carryforwards Net operating losses Deferred Tax Assets Operating Loss Carryforwards Foreign Foreign net operating loss carryforwards Deferred Tax Assets Tax Credit Carryforwards Tax credit carryforwards Tax credits Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost Stock based compensation Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Reserves Other reserves and accrued liabilities Deferred Tax Assets Valuation Allowance Less: valuation allowance Deferred Tax Liabilities, Subject to Expiration Deferred Tax Liabilities Subject To Expiration Gross liabilities to expire in 2013 Defined Benefit Plan Contributions By Employer Contributions made under defined contribution plan Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Depreciation Depreciation expense Depreciation And Amortization Depreciation and amortization Derivative By Nature [Axis] Derivative, by Nature Derivative Contract Type [Domain] Derivative Contract Type [Domain] Derivative Fair Value Of Derivative Liability Warrant derivative liability, fair value Derivative Financial Instruments Liabilities Fair Value Disclosure Warrant derivative liability Derivative Instrument [Member] Derivative Instrument [Member] Derivative Instrument Derivative Instrument Risk [Axis] Derivative Instrument Risk [Axis] Derivative Instruments And Hedging Activities Disclosure [Text Block] Warrants and Warrant Derivative Liability Derivative Liabilities Warrant derivative liability Derivative Liabilities Noncurrent Ending Balance Beginning Balance Derivative liability Fair value of derivative liability Derivative Liabilities Transferred to Stockholders' Equity Derivative Liabilities Transferred To Stockholders Equity Transfers to equity Derivative [Line Items] Derivative [Line Items] Derivative Name [Domain] Derivative, Name [Domain] Derivatives Embedded Derivatives Long Term Debt Redemption Feature Derivatives Fair Value [Line Items] Derivatives, Fair Value [Line Items] Derivatives Policy [Text Block] Derivative Instruments Derivative [Table] Derivative [Table] Development Fees Committed Development Fees Committed Development fees committed Disclosure - Accrued Expenses [Abstract] Disclosure Accrued Expenses [Abstract] Disclosure - Accrued Expenses [Abstract] Disclosure - Assets and Liability Measured at Fair Value on Recurring Basis [Abstract] Disclosure Assets And Liability Measured At Fair Value On Recurring Basis [Abstract] Disclosure - Assets and Liability Measured at Fair Value on Recurring Basis [Abstract] Disclosure - Assumptions Used to Estimate Fair Value of Share-Based Payment Awards [Abstract] Disclosure Assumptions Used To Estimate Fair Value Of Share Based Payment Awards [Abstract] Disclosure - Assumptions Used to Estimate Fair Value of Share-Based Payment Awards [Abstract] Disclosure - Change in Fair Value of Warrant Derivative Liabilities [Abstract] Disclosure Change In Fair Value Of Warrant Derivative Liabilities [Abstract] Disclosure - Change in Fair Value of Warrant Derivative Liabilities [Abstract] Disclosure Commitments And Contingencies Additional Information [Abstract] Disclosure Commitments And Contingencies Additional Information [Abstract] Disclosure Commitments And Contingencies Additional Information [Abstract] Disclosure - Components of Loss from Operations Before Taxes [Abstract] Disclosure Components Of Loss From Operations Before Taxes [Abstract] Disclosure - Components of Loss from Operations Before Taxes [Abstract] Disclosure Debt Additional Information [Abstract] Disclosure Debt Additional Information [Abstract] Disclosure Debt Additional Information [Abstract] Disclosure - Defined Contribution Plans - Additional Information [Abstract] Disclosure Defined Contribution Plans Additional Information [Abstract] Disclosure - Defined Contribution Plans - Additional Information [Abstract] Disclosure - Difference between Benefit from Income Taxes and Amount Computed by Applying Statutory Income Tax Rate to Income Before Taxes [Abstract] Disclosure Difference Between Benefit From Income Taxes And Amount Computed By Applying Statutory Income Tax Rate To Income Before Taxes [Abstract] Disclosure - Difference between Benefit from Income Taxes and Amount Computed by Applying Statutory Income Tax Rate to Income Before Taxes [Abstract] Disclosure Equity Additional Information [Abstract] Disclosure Equity Additional Information [Abstract] Disclosure Equity Additional Information [Abstract] Disclosure - Estimated Useful Lives [Abstract] Disclosure Estimated Useful Lives [Abstract] Disclosure - Estimated Useful Lives [Abstract] Disclosure - Expense Benefit from Income Taxes [Abstract] Disclosure Expense Benefit From Income Taxes [Abstract] Disclosure - Expense Benefit from Income Taxes [Abstract] Disclosure Future Minimum Lease Payments [Abstract] Disclosure Future Minimum Lease Payments [Abstract] Disclosure Future Minimum Lease Payments [Abstract] Disclosure - Income Tax Effect of Each Type of Temporary Difference Comprising Net Deferred Tax Asset [Abstract] Disclosure Income Tax Effect Of Each Type Of Temporary Difference Comprising Net Deferred Tax Asset [Abstract] Disclosure - Income Tax Effect of Each Type of Temporary Difference Comprising Net Deferred Tax Asset [Abstract] Disclosure Income Taxes Additional Information [Abstract] Disclosure Income Taxes Additional Information [Abstract] Disclosure Income Taxes Additional Information [Abstract] Disclosure Intangible Assets [Abstract] Disclosure Intangible Assets [Abstract] Disclosure Intangible Assets [Abstract] Disclosure Intangible Assets Additional Information [Abstract] Disclosure Intangible Assets Additional Information [Abstract] Disclosure Intangible Assets Additional Information [Abstract] Disclosure - Intangible Assets Estimated Amortization Expense [Abstract] Disclosure Intangible Assets Estimated Amortization Expense [Abstract] Disclosure - Intangible Assets Estimated Amortization Expense [Abstract] Disclosure Inventory [Abstract] Disclosure Inventory [Abstract] Disclosure Inventory [Abstract] Disclosure - Jurisdictions Subject to Tax Examinations [Abstract] Disclosure Jurisdictions Subject To Tax Examinations [Abstract] Disclosure - Jurisdictions Subject to Tax Examinations [Abstract] Disclosure Nature Of Business And Basis Of Presentation Additional Information [Abstract] Disclosure Nature Of Business And Basis Of Presentation Additional Information [Abstract] Disclosure Nature Of Business And Basis Of Presentation Additional Information [Abstract] Disclosure Of Compensation Related Costs Share Based Payments [Text Block] Stock Incentive Plans and Stock Based Compensation Disclosure Property Plant And Equipment [Abstract] Disclosure Property Plant And Equipment [Abstract] Disclosure Property Plant And Equipment [Abstract] Disclosure - Property Plant Equipment - Additional Information [Abstract] Disclosure Property Plant Equipment Additional Information [Abstract] Disclosure - Property Plant Equipment - Additional Information [Abstract] Disclosure - Quarterly Summarized Financial Information [Abstract] Disclosure Quarterly Summarized Financial Information [Abstract] Disclosure - Quarterly Summarized Financial Information [Abstract] Disclosure Reconciliation Of Total Amounts Of Unrecognized Tax Benefits [Abstract] Disclosure Reconciliation Of Total Amounts Of Unrecognized Tax Benefits [Abstract] Disclosure Reconciliation Of Total Amounts Of Unrecognized Tax Benefits [Abstract] Disclosure Related Party Transactions Additional Information [Abstract] Disclosure Related Party Transactions Additional Information [Abstract] Disclosure Related Party Transactions Additional Information [Abstract] Disclosure Significant Accounting Policies Additional Information [Abstract] Disclosure Significant Accounting Policies Additional Information [Abstract] Disclosure Significant Accounting Policies Additional Information [Abstract] Disclosure - Stock Based Compensation Expense [Abstract] Disclosure Stock Based Compensation Expense [Abstract] Disclosure - Stock Based Compensation Expense [Abstract] Disclosure - Stock Incentive Plans and Stock Based Compensation - Additional Information [Abstract] Disclosure Stock Incentive Plans And Stock Based Compensation Additional Information [Abstract] Disclosure - Stock Incentive Plans and Stock Based Compensation - Additional Information [Abstract] Disclosure Stock Option Activity [Abstract] Disclosure Stock Option Activity [Abstract] Disclosure Stock Option Activity [Abstract] Disclosure Summary Of Restricted Stock Activity [Abstract] Disclosure Summary Of Restricted Stock Activity [Abstract] Disclosure Summary Of Restricted Stock Activity [Abstract]